Pumping apparatus for lapping machine



Feb. 17, 1959 G. w. THOMPSON, JR 2,873,563

PUMPING APPARATUS FOR LAPPING MACHINE Filed Nov. 14, 1956 2 Sheets-Sheet 1 Fla. 1

INVENTOR- GEORGE W. THOMPSONHR.

Wax/1e ys Feb. 17, 1959 G. w. THOMPSON, JR 2,873,563

PUMPING APPARATUS FOR LAPPING MACHINE Filed Nov. 14, 1956 2 Sheets-Sheet 2 INVENTOR.

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GEonaEW. THoMPsoNJR.

United States Patent 2,873,563 PUMPING APPARATUS FOR LAPPING MACHINE George W. Thompson, Jr., West Allis, Wis., assignor to Empire Corporation, West Allis, Wis., a corporation of Wisconsin Application November 14, 1956, Serial No. 622,069

4 Claims. (Cl. 51-463) This invention relates to a lapping machine of the type generally employed for lapping the ends of tungsten carbide tool bits and the like, and more particularly to a pumping apparatus for circulating an abrasive suspension used in the lapping operation.

Lapping machines are generally provided with a rotary, flat lapping plate and the workpieces are generally floated on the lapping plate while retained in a workholder. Each workholder is held against travel with relation to the lapping plate by a yoke which bears against the workholder.

An abrasive suspension or slurry which consists generally of an abrasive material suspended in a lubricant such as oil, is continually applied to the lapping surface of the lapping plate. In the normal use of a lapping machine the abrasive suspension is discarded after use due to the difficulty in transporting and pumping an abrasive viscous material.

The present invention is directed to a pumping apparains for recirculating a viscous abrasive suspension for use in a lapping machine or the like. According to the invention, the abrasive suspension is conducted after use on the lapping plate to the lower end of a housing which constitutes a sump. A pump disc is mounted for rotation within the housing and a portion of the periphery of the disc is disposed within the sump and rotates within the abrasive suspension contained in the sump. The rotating pump disc picks up the viscous abrasive suspension and the suspension is removed from the upper portion of the disc by a tube and conducted through the tube to the lapping surface of the lapping plate.

This construction provides for a continuous recirculation of the abrasive suspension so that the suspension may be reused indefinitely.

In order to prevent the abrasive material from contacting the bearings of the drive shaft adapted to rotate the pump disc, a drip shield is provided in the housing which directs the unused portion of the abrasive suspension which is not removed from the disc by the tube away from the drive shaft and back to the sump. In addition to the drip shield, bafiles are employed in connection with the shaft to provide a tortuous route for the movement of the abrasive suspension into the bearings.

The pumping disc employed to lift the abrasive suspension is a simple and inexpensive means of moving a viscous abrasive material. There are no wearing parts in the structure and the operation of the pump disc also serves to agitate the abrasive suspension and prevent settling of the abrasive material.

Other objects and advantages of the invention will appear in the course of the following description.

The drawings illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

Figure 1 is a perspective view of the lapping machine with parts broken away and sectioned;

Fig. 2 is a vertical section of the lapping machine;

Fig. 3 is an enlarged fragmentary vertical section showing the structure of the pump disc and the tube;

Fig. 4 is an end view of the lapping machine with parts broken away and sectioned; and

Fig. 5 is a fragmentary top view of the pumping disc and the tube employed to remove the abrasive suspension from the disc.

The lapping machine illustrated comprises a housing 1 having a circular depression and generally flat upper surface to provide a drip pan 2 with the bottom of the drip pan slanting toward an outlet drain 3.

A lapping plate 4 is horizontallymounted in the depression in the top of the housing on a verticalshaft 5 which is rotatable in a central bearing 6 in the bottom of pan 2.

The top of lapping plate 4 is provided with a plurality of radial slots or grooves 7 separating the upper lapping surface into equal segments. A central circular recess 8 in the top of plate 4 serves to provide an inner circular edge for the lapping surface which is concentric with the outer circumferential edge of the lapping surface.

The lapping plate 4 is driven by a motor 9 which is dis posed in housing 1. The motor is driven through a worm gear 10 on the motor shaft and a corresponding gear 11 on the lower end of shaft 5.

One or more circular workholders 12, there being three illustrated in the drawings, are provided with workpieces 13 extending downwardly through corresponding circumferentially spaced openings in the workholder. The workpieces 13 are shown as square rods having flat tungsten carbon lower ends arranged in a common plane to rest on top of plate 4.

The workpieces 13 are suitably secured within the workholder l2 and serve to maintain the workholder above and out of contact with the lapping surface of plate 4 at all times.

The workholders 12 are prevented from rotating with the lapping plate 5 and are located thereon for individual rotation by means of yokes 14, there being one yoke for each workholder 12.

Each yoke 14 is adjustably mounted and secured in place on a vertical stud 15 which is threaded into a depending boss 16 on the undersurface of the upper wall of housing 1 adjacent the plate 4. The stud 15 carries a hand knob 17 on its upper end for convenience in adjust ing the yoke.

When the lapping plate 4 is rotated in a given direction each of the workholders 12 will rotate on its own vertical axis in the same direction as the lapping plate. The driving force for rotating the workholders arises from the differential in rotational speed of that portion of the lapping plate 4 engaged by the outer half of the workpieces as against the slower rotational speed for that. portion of the lapping plate 4 engaged by the inner half of the workpieces.

An abrasive suspension or slurry is continually supplied to the lapping surface of plate 4 and is adapted to be recirculated for reuse. For this purpose, housing 1 is provided with a recess 18 at one end and the recess functions as a pumping chamber. The outer end of the pumping chamber 18 is closed off by a generally circular plate 19. The drain outlet 3 communicates with the pumping chamber 18 and the lower end of the pumping chamber defines a sump 20 in which the abrasive suspension is collected. The abrasive suspension is gen erally a viscous suspension of an abrasive material in a lubricant, such as oil or the like.

A pumping disc 21 is disposed within the pumping chamber and is adapted to lift the abrasive suspension to a discharge tube 22 extending from the upper portion of the chamber 18 to a position over the top of the lapping plate 4 where the abrasive suspension drips regularly ontothe lapping surface. The discharge tube 22 is suitably secured within an openingin the housing 1 and is disposed at a slight incline so that the abrasive Patented Feb. 17, 1959.

states g suspension will moveth-rough the tube to the lapping plate by gravity.

The pumping disc 21 is of a substantially large diameter and is mounted on a horizontal drive shaft 23 which extends through an opening in the wall 24 of housing 1. The shaft 23 is driven by a motor'25 through a suitable gear reduction 2h.

The inner side of the pumping disc 21 adjacent the peripheral edge as indicated by 27 is machined. The surface 27 is disposed to pass close to the inner end of tube 22 and the latter is disposed in a plane substantially parallel to the surface 27 so that the tube 22 continuously scrapes the highly viscous layer of the abrasive suspension on the surface 27 and picks off a given amount of the material from the disc.

As best shown in Fig. 5, the forward half of the inner end of the tube 22 is notched or recessed, as indicated by 22a. The notch 22a faces away from the direction of rotation of pumping disc 2i. and in effect functions as a scoop to direct the abrasive suspension into the tube 22.

The thickness of the layer of the viscous abrasive suspension on surface 27 is greater than the spacing of the notch 22a from the surface so that the suspension rotating with disc 21 engages the rear unnotched portion of tube 22 and is directed downwardly within the tube as shown in Fig. to the lapping plate 4.

The outer side of the pump disc 21 has a plurality of agitator blades 28 which are formed integrally with the disc and are adapted to continuously dip into and agitate the abrasive suspension in the sump so that the abrasive does notsettle or stratify.

The pumping apparatus of the invention has no frictional wearing parts and can be said to merely lift the abrasive suspension to the tube 22 from which it drips onto the lappingsurface of plate 4. The abrasive suspension then drops into the grooves 3 in the plate 4 and from there it passes into pan 2 from which it drains back into the sump v20 through drain outlet 3.

In order to prevent the abrasive suspension from entering the motor shaft bearings, a drip shield 29 is secured to the outer surface of wall 24 beneath the tube 22. The drip shield 29 is provided with a generally arcuate shape and the upper edge 30 of the shield is tapered so that the suspension dripping downwardly from the tube will fall onto the drip shield and be directed along the wall 24 and around the motor shaft 23 to the sump 20.

In addition to the drip shield 29, the abrasive suspension is prevented from entering the motor shaft bear- The baffle arrangement ings by a baffle arrangement. includes an embossrnent 31 formed on the inner surface of the pump disc 21. A central recess 32 is formed in the embossment and the recess is provided with inwardly diverging walls. A bushing 33 having an outwardly diverging end portion is disposed around the motor shaft 23 and is secured by a press fit within an opening in wall 24. The diverging outer end portion of bushing 33 is received within the recess 32 in the pump disc and is spaced from the walls of the recess 32 to provide a clearance therebetween. Any abrasive suspension which may pass between the wall 24 and the embossment 31 would be thrown outwardly within the clearance away from the shaft 23.

A further measure for preventing the abrasive material from entering the motor shaft bearings is provided by an oil slinger 34 :which is secured by a press fit to theshaft 23 inwardly of the housing wall 24. The oil slinger rotates with the shaft and serves to sling any abrasive particles outwardly from the shaft by the can trifugal action of the rotating members.

The present invention provides a simple and efficient apparatus for recirculating a viscous abrasive suspension used in a lapping operation. The pumping apparatus has no wearing parts and can be used for extended periods with a minimum of maintenance.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In a lapping mach ne, an apparatus for recirculating an abrasive suspension which comprises, a sump to contain an abrasivemixturc, a disc mounted for rotation about the central axis thereof and disposed with portion of the periphery thereof within said sump, means for rotating said disc through said sump with said mixture adhering to'the disc and being lifted from the sump, tubular means disposed outside of the sump for removing said mixture from the disc and conducting said mixture to the lapping surface of the lapping machine, and means connected to a side surface of the disc and extending outwardly from said surface in an axial direction for continually agitating the mixture within the sump while the disc is rotating.

2.111 a lapping machine, a housing with the lower end portion of said housing defining a sump for the collec'tion of an abrasive suspension, 2. drive shaft extending through an opening in said housing, a disc mountedon saidshaft and disposed with a portion of the periphery thereof within said sump, means for rotating said shaft to correspondingly rotate said disc through the sump, said suspension adhering to the rotatingdisc and being lifted from the sump, means disposed within the upper portion of the housing for removing a portion of the suspension from the disc and conducting the same to a c t on o u e a d defle in mean s t htl housing and disposed-beneath said last named means ifor directing the excess suspension away from the shaft and back to the sump.

3. In a lapping machine, a housing with the lower end portion of said housing defining a sump for the collection of an abrasive suspension, 2. drive shaft extending through an opening in said housing, a disc mounted on said shaft and disposed with a portion of the periphery thereof Within said sump, means for rotating said shaft to correspondingly rotatesaid disc through the sump, said suspension adhering tothe rotating disc and being lifted from thesump, meansdisposed withinthe upper portion of the 'housingfor removing a portion of the suspension from the disc and conducting the same to a location of use, a generally arcuate drip shield secured to the housing at a location above said shaft and disposed to direct the excess suspension around the shaft and back to the sump, and baffie means associated with the shaft to provide a circuitous route for the passage of any suspension along the shaft to the shaft bearings.

4. in alapping machine, a housing with the lower end portion of said housing defining a sump for the collection of an abrasive suspension, a drive shaft extending through an opening in said housing, a disc mounted on said shaft and disposed with a portion of the periphery thereof within said sump, means for rotating said shaft to correspondinglyrotate said disc through the sump, said suspension adhering to the rotating disc and being lifted from the sump, means disposed within the upper portion of thehousing forremoving a portion of the suspension from the disc and conducting the same to a location of use, and at least one paddle member secured to a side surface of the disc and extending to substantially adjacent the peripheral edge of said disc, said paddle member serving to continually agitate the suspension Within the sump while the disc is rotating.

References cited in the file of this patent UNITED STATES PATENTS Luther e Feb. ,8, 1881 

